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Data.gov Infrastructure as Code
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Volume swapping with Auto-scaling Group #4

Open JJediny opened 7 years ago

JJediny commented 7 years ago

How to swap block storage with an auto-scaling group without downtime?

looking like the suggested approach is to use aws_volume_attach in terraform to reattach the persistent volume to the new AMI and use an inline provisioner to perform the mount - https://github.com/hashicorp/terraform/pull/2050#issuecomment-125229024.

:thinking_face: find it hard to see how that approach works without downtime as you have to detach the volume from the old instance serving traffic and then attach/mount it to the new instance...

Via Terraform inline provisioner

https://www.terraform.io/docs/provisioners/remote-exec.html

Via Python?

https://github.com/dizzythinks/asg_persistence/blob/master/attach_volume.py https://cloudinit.readthedocs.io/

Via Ansible?

pre_tasks:
- name: format the extra drive
  filesystem:
    dev: /dev/xvdb
    fstype: ext4

- name: mount the extra drive
  mount:
    name: /secondary
    # ubuntu renames the block devices to xv* prefix
    src: /dev/xvdb
    fstype: ext4
    state: mounted